Adding drone model to Gazebo simulation

Follow the official CTU-MRS guide for the full step-by-step process: Adding a custom drone to the simulation

Tips & tricks

Model files & meshes

Keep the model as simple as possible. Meshes exported straight from CAD are usually far more detailed than the simulation needs, and the extra triangles just increase rendering demand — the visual/collision geometry only has to look right, not be manufacturing-accurate.

Run the mesh through a decimation process before importing it (e.g. Blender's Decimate modifier or meshlab) to cut the triangle count down while keeping the overall shape recognizable.

PX4 airframe

The .main.mix mixer files described in the official guide are legacy — the ros2 branch of the CTU-MRS repos already correctly uses the more modern PX4 Control Allocation system instead. Instead of an airframe file that just points at a .main.mix file:

# airframes/4001_my_drone
#!/bin/sh
. ${R}etc/init.d/rc.mc_defaults
set MIXER quadrotor_x

rotor geometry and spin direction are defined directly in the airframe file via CA_ROTORx_PX/PY/PZ/CT/KM params, and there is no separate ROMFS/px4fmu_common/mixers/*.main.mix file:

#!/bin/sh
. ${R}etc/init.d/rc.mc_defaults

PX4_SIMULATOR=${PX4_SIMULATOR:=gz}
param set-default SIM_GZ_EN 1
param set-default MAV_TYPE 13          # hexarotor
param set-default CA_AIRFRAME 0
param set-default CA_ROTOR_COUNT 6

param set-default CA_ROTOR0_PX 0
param set-default CA_ROTOR0_PY 0.462
param set-default CA_ROTOR0_PZ -0.0115
param set-default CA_ROTOR0_CT 1.0
param set-default CA_ROTOR0_KM -0.06
# ... CA_ROTOR1..5 the same way

param set-default SIM_GZ_EC_FUNC1 101  # map rotor to a Gazebo ESC output
# ...
param set-default SIM_GZ_EC_MIN1 0     # use the full 0-1000 range
param set-default SIM_GZ_EC_MAX1 1000  # for the best signal resolution

param set-default BAT1_N_CELLS 6
param set-default BAT1_CAPACITY 16000
param set-default MPC_THR_HOVER 0.57

The CA_ROTORx_PX/PY/PZ positions and CA_ROTORx_KM spin direction sign must match the motor geometry defined in the model's sdf.jinja — if they don't, the thrust allocation won't line up with the visual/physical model. SIM_GZ_EC_FUNCx/MIN/MAX additionally map each rotor to a Gazebo ESC output channel, which the legacy mixer approach didn't need to handle explicitly.